The main objective of this proposed study is the investigation of plasma membrane glycoconjugate metabolism in metastatic and nonmetastatic mammalian mammary tumors including human metastatic mammary tumor cells grown in tissue culture. Cells will be treated with neuraminidase and galactose oxidase prior to radiolabeling with (3H)-sodium borohydride (Gahmberg et al., J. Cell Biol. 68. 642. 1976). The localization and metabolic fate of this labeled cell surface material will be assessed in vitro. Internalization and reutilization of labeled cell surface material will be monitored with electron microscope autoradiography while plasma membrane shedding of this material will be quantitated by use of scintillation counting methods. Labeled cell surface material (glycoprotein and glycolipid) and shed cell surface material will be characterized by use of sodium dodecylsulfate polyacrylmide slab gel electrophoresis, paper chromatography and thin layer chromatography. Electron microscope autoradiographs of labeled cells have shown that the majority (approximately 70%) of grain associated with (3H)-galactose are located over the plasma membrane. The grain distribution does not change appreciably within 24 hours after radiolabeling although significant quantities of acid soluble material is released from these cells into the culture medium. The majority of this shed material is free galactose which may be hydrolized from the cell surface by ectoglycosidases.